An ignition system of an internal combustion engine comprises an ignition coil assembly that supplies a high voltage electric current to a spark plug, for example: “Coil-on-Plug”, and the ignition coil assembly includes an ignition coil, which is mounted directly on each of the spark plug to provide the advantages of the elimination of high voltage leads, simple and easy installation. The ignition coil assembly includes a conventional metallic coil spring type conductor to conduct the high voltage electric current from the high voltage coil terminal of the ignition coil to the electrode terminal of the spark plug. The recognized performance problem of such an ignition coil assembly includes the misfire which arises from the deterioration of the electrical conductivity of the metallic coil spring upon performance ageing, which leads to a gradual increase in the fuel consumption and emissions in conjunction with the loss of vehicle power. This is associated with the inferior corrosion resistance of the metallic coil spring under the harsh application conditions of combined high temperature and humidity environment. The other drawback of the metallic coil spring includes the possibility of dielectric failure due to the induction of electro-magnetic field concentration. It is an object of at least one embodiment of this invention to address these drawbacks of a typical ignition coil assembly that includes the metallic coil spring.